You must find the junction of the 12 wires for the fridge and the furnace. It will be under the fridge or behind it or in some close by cabinet. My trailer had the furnace, fridge, range hood, and water heater controls on the same circuit. 3 wires cam together next to the furnace under the fridge, It's not outside it is inside the cabinetry. You just gonna have to keep looking.
A loose connection starts at the factory. Not going down the road. A loose connection causes heat which causes a high resistance connection.
2011 Keystone Sprinter 323BHS. Retired Master Electrician. All Motor Homes are RV's. All RV's are not Motor Homes.